Method of producing acetyl cellulose



. ance with the viscosit product.

Patented Feb. 24, 1931 UNITED STATES PAT ENT o FIc SAMUEL rsrnoon YVLES AND LOUIS DE noor, or ARNHEM, NETH RLAN S, Assienons 'ro ALGEMEENE KUNSTZIJDE UNIE iv. v., or Anni- BM, NETHERLANDS METHOD OF PRODUCING ACETYL CELLULOSE No Drawing. Application filed December 16, 1926, Serial No. 155,332, 7 24, 1925. 1

Our invention relates to a method of producing acetyl cellulose compounds.

It is known that one of the most important requirements to be satisfied by a good spin: ing solution is viscosity. A high degree of viscosity of the spinning solution generally results in the filaments to be produced therefrom being very strong; the lustre is also improved by an increased viscosity and spinning takes place more easily.

Hitherto however for producing an increased viscosity attention has been concentrated almost exclusively upon the proportions in which the various constituents of the acetylating mixture are mixed and their quantity as well as that of the catalyst used has been adapted to suit the content of moisture in the cellulose.

After continued experiments We have found however that the desired object can be obtained in a much simpler manner, While the viscosity of the acetyl compounds can be more exactly controlled than is the case With the usual methods.

The method according to our invention is characterized in this that before acetylation, the water content of the acetylating bath or of the catalyst (s) to be used in the acetylation or of both is adjusted exactly in accordof the desired final water and water vapour being excluded.

Further, our invention comprises a method whereby the acetylating bath either previously treated in the manner referred to or without preliminary treatment, is mixed With the catalyst (s), and thereupon left standing for some time with the exclusion of Water and water vapour.

Finally it is possible according to our invention to cause the acetylating bath or acetylating mixture previously treated in the and. inthe-Netherlands December manner referred to, to act upon cellulose, the water content of which has been exactly adjusted beforehand.

When reference is made in the specification and claims to acetylating-bath this is to be understood asthe actual acetylating agent, such as for instance acetic anhydride mixed with suitable diluents, such as glacial acetic acid and the like. The catalysts in question are: sulphuric acid, sulphury-l chloride, methylamine sulphate and other substances usually employed as well as mixtures of two or more of these substances.

In thespecification and the claimsthe ex-v pression cellulose includes, besides cellulose, alsocellulose hydrate and other near con- 1 version products of cellulose such as. commonly in use in the artificial silk industry.

I By applying our inve'ntiomthe Water content oantherefore be regulated very exactly,

, hus resulting in very much improved ac'ety-- lation products and consequently-in, much better final products. According to our invention it is'possible to, prevent undesirable amounts of-wa-ter exerting upon the reaction an influence which causes the acetylation to adopt a definite course or produces by-reac: tions which are undesirable-forobtaining a satisfactory product. I

Moreover the valuable advantage is obtained that by employing our invention, slight variations in temperature have less detrimental results. This. again facilitates the acetyla-tion to a considerableeXt-ent and causes it to progress more regularly.

If the method according to. our invention is carried out in such a manner that the acetyl-atingagent is practically entirely anhydrous, before the same is caused to act upon the cellulose, it is possible by correctly choosing th'e'water content of the cellulose employed to control the acetylation"reaction to a very definite extent and consequently to control to a greater extent the nature of the resulting final products. The cellulose used can consist of the materials usual for this purpose and may be subjected if desired to a preliminary treatment.

The following examples give some .of the many Ways in which. our invention can be used; it is to be understood however, that several alterations may be applled Without departing from the scope of our invention.

Ewample I 4 kg. acetic anhydride are mixed-with L5 kg. glacial acetic acid'and this mixture is left standing for about 6 hours. 60 g. sulphuryl chloride are'then added as condensation agent, whereupon the'mixture is allowed to stand again for a few hours, care being taken, as in the first instance, that water or water vapour is excluded. 1 kg. cellulose having a moisture content of 6% is then immersed in the mixture produced in the manner referred to. The acetylation-takes place at 60 C. and requires about 6 hours. The solution produced in this way is worked up in a known manner, either by precipitatingthe resulting cellulose compound, dissolving in a volatile solvent and spinning in an atmosphere which may be heated if desired, or by directly spinning the solution in a suitable precipitating bath or by working up into plastic masses.

Ewample [I As a general rule the quantities of the acetic anhydride, glacial acetic acid and condensation agent, as Well as the moisture content of the cellulose and the time during which the mixture is left standing are chosen to correspond with the desired viscosity of the acetate solution. may be said that the greater-the desired viscosity the longer should the mixture be left standing. The most highly viscous solutions are produced When use is made of an acetylating bath which has been left standing for a very long time for instance 10 hours, so that practically the last traces of water in the acetic acid have combined with the acetic anhydride. As already mentioned in the foregoing, the viscosity of the products is of very great importance.

Themethod according to our invention which'enables the viscosity to be adjusted arbitrarily to an extremely exact degree is thereforeof greatest importance for the acetate silk indnstry. lVe claim:

'1. The method of producing acetyl cellul0se comprising providing an acetylizing bath consisting of acetic acid anhydride and glacial acetic acid, permltting said bath'to stand for several hours until a part of the As a general rule it Water in the acid has combined with the anhydride and subsequently introducing the cellulose into said bath.

2. The method of producing acetyl cellulose comprising providing an acetylizing bath-consisting of acetic acid anhydride and glacial acetic acid, permitting said bath to stand for several hours until a part of the water in the acid'has combined with the anhydride, then introducing a catalyzer and subsequently introducing the cellulose into said bath.

3. The m-ethod'of producing acetyl cellulosecomprising providing an acetylizing bath consisting of acetic acid anhydride and glacial acetic acid. pcrmitting said bath to stand for several hours until a part of the water inthc acid has cornbinedwith the anhydride, then introducinga catalyzer then allowing the bath to stand for several more hours and then introducing the. cellulose into sald bath. V

in testimony whereof we affix our signatures.

S. I. VLES. L. DE HOOP. 

